学位の種類: 博士（農学）. 報告番号: 甲第4198号. 学位記番号: 新大院博（農）甲第159号. 学位授与年月日: 平成28年3月23日Biological control, especially with Bacillus-based agents, offers an attractive alternative to the use of synthetic pesticides for sustainable management of white mold caused by Sclerotinia sclerotiorum. In this study, S. sclerotiorum isolates were characterized based on morphology and internal transcribed spacer sequences, followed by an assessment of their pathogenicity. Additionally, eight Bacillus samples were isolated from rhizospheric soil as potential biocontrol agents. Molecular analyses of 16S rDNA and gyrase subunit A (gyrA) genes combined with cultural and biochemical analyses confirmed that all isolates were Bacillus amyloliquefaciens subsp. plantarum. The production of hydrolytic enzymes by the isolates, and their plant growth-promoting attributes were assessed. Molecular analyses of eight antibiotic genes revealed that the genomes of all of the Bacillus isolates included bacA (bacilysin), dfnM (difficidin), fenA (fengycin), ituA (iturin), and sfp (surfactin) genes. The Bacillus isolates inhibited mycelial growth and suppressed the formation of sclerotia in an in vitro test. Treatment with the Bacillus isolates also resulted in mycelial deformities and cell wall lysis, abnormalities in apothecia, and ungerminated ascospores according to light microscopy and scanning electron microscopy analyses. These results suggest that the bacterial isolates are highly antagonistic against S. sclerotiorum. Additionally, seed bacterization with the Bacillus isolates protected mustard seedlings against S. sclerotiorum infection by up to 98%. In pot experiments, disease symptoms in mustard plants treated with a foliar spray containing Bacillus isolates decreased by up to 90%. Furthermore, the bacterial isolates increased mustard seed germination rates and improved seedling vigor, suggesting they have plant growth-promoting activities.